After retooling the series in 2014 with a brand new cast and a grittier, darker tone, Michael Bay is pushing Transformers to its limits with his fifth and final entry in the franchise. Based on the trailer, Transformers: The Last Knight will be by far the darkest movie of the pentalogy, with Optimus Prime turning evil.

SEE ALSO: The five biggest announcements from PSX 2016

The official synopsis for the upcoming sequel has yet to be revealed, but the trailer makes it clear that The Last Knight picks up shortly after the events of Age of Extinction. Mark Wahlberg is still the star, Bumblebee still features prominently and, at least in the beginning, Optimus is still floating through space:

Unlike previous Transformers movies (or the cartoons, for that matter), there appears to be a Nazi flag in The Last Knight. I’m assuming this has something to do with the history of the planet and the origin of whatever MacGuffin Megatron will be looking to steal from Earth this time around, but it is a bit jarring.

The rest of the trailer is a mess of action and explosions (what else would you expect?), but in the final moments, we see that Optimus Prime has returned to Earth. Whatever happened to him in space has him ready to kill both Cade Yeager (Mark Wahlberg) and Bumblebee, though his apology suggests that he either can’t control himself, or that his actions serve some greater good we don’t know about.

Transformers: The Last Knight hits theaters on June 23rd, 2017.